The present invention relates to an electronic device having high-density wiring, and more particularly to an electronic device having high-density wiring in which the shape or configuration of wiring in a digital electronic device is dealt with.
As advances in electronic devices are developed, emphasis towards further miniaturization, complexity and large scale integration schemes will become more prevalent as the demands for high function and high performance become increased, thereby facilitating use of and portability of the electronic device. Employing a high-density wiring technique greatly contributes to attainment of these objectives.
Wiring in the electronic device is mainly formed on a printed wiring board, a ceramic board, a semiconductor or the like, and in either case, the wiring is usually designed on the condition that the configuration thereof, such as width and thickness of a conductor, for use in wiring, is fixed, except for the length of the conductor thereof. Particularly, the number of conductors for use in wiring for transmitting signals is increased and, accordingly, it is common that the above condition is strictly kept since the design of wiring is simplified by using this condition.
When the width and thickness of a conductor, used in wiring, are standardized to be fixed and conductors are positioned on grids arranged at regular intervals, the design of wiring can be made simply and rapidly by dividing the design into designs relative to paths and shape of conductors. More particularly, the path design can be made only by considering how conductors can be connected between terminals through predetermined paths on the grids without intersection with many other conductors. The shape design can be made only by applying a width of conductors, a shape of connection terminals and a shape of through-holes and the like to the result of the path design to design actual shape of conductors. A final wiring configuration is described on a mask which is subjected to a process technique, such as the photolithography and the etching technique, to form actual wiring.
Such a wiring design method is known widely and can be found in, for example, "HIGH-DENSITY SURFACE MOUNTING TECHNIQUE", TRICEPS Corporation, ISBN 4-88657511, pages 73 and 126-128, and "CAE OF PRINTED BOARD" by Akihiko Yamada, Applied Technique Publishing Corporation, pages 4-5, 58-59 and 76.
As described above, by standardizing to make the width and thickness of conductors fixed and dividing the wiring design into two steps of the path design and the shape design, the design work of wiring can be arranged to be concise and be made rapidly or a large-scale design can be achieved to contribute to the development of the electronic industry greatly.
An electronic device can be complicated, formed on a large scale and miniaturized and hence possess increased functions and high performance by high-density wiring. More particularly, there is technical development of the process which can form a wiring configuration for conductors and through-holes with high density, so that wiring can be made narrower and thinner and the mounting density can be improved to attain miniaturization, enhanced circuit complexity, large-scale formation and high function of the electronic device. Further, since miniaturization of the device can shorten the length of wiring, a time required for propagating a signal through wiring is reduced so that the device is operated at high speed to thereby improve the performance of the device.
In the device design using the high-density wiring, particularly the wiring design, the dimension of wiring is standardized to be narrowed and thinned to a minimum attained by the high-density wiring technique. Consequently, the dimension of wiring is reduced uniformly. This method advantageously reduces the wiring dimension of the device and hence the mounting density uniformly over the whole device to utilize the benefit of the high-density wiring technique effectively.
As described above, in the prior art, the dimension such as the width and thickness of conductors is designed in accordance with the predetermined standards and the high-density wiring is attained by reduction of the standardized dimension to thereby realize miniaturization circuit complexity, large-scale formation, high function and high performance of the electronic device.
However, any attempt at further advancement using the above conventional wiring method would reach an electrical limit, so that the normal operation of the electronic circuit is impeded. This is caused by the fact that narrowed and thinned wiring configuration with high density reduces a sectional area of conductors and increases an electrical resistance of conductors. More particularly, when the conventional wiring method is used to narrow and thin the width and thickness of conductors, a resistance of conductors is increased and the electronic device can no longer be operated normally or the performance of the device is reduced. It would not be practical to solve this problem by improvement of material since a material having a considerably small resistivity as compared with copper or aluminum is not available and since the superconductor wiring cannot be easily utilized. Further, in the conventional wiring design technique, since the dimension, such as the width and thickness of conductors, is standardized to be fixed, malfunction of the electronic device and reduction of performance thereof are caused by employing many long conductors.